From day one we didn’t want to use complex and cryptic protocols so we chose xmlrpc for our communication channel. It was easy to implement, had wide support in php and python and was very easy to debug. We knew that at some point we would need to switch to a more efficient protocol, but we didn’t know it was going to be so soon.

After doing some extensive benchmarking we realize that the through output of the protocol was very low, not only that, if too many xmlrpc connections were spawned it would eventually consume all resources of the process (file descriptors, sockets and memory). This was a painful lesson to learn, but we did. So we switched to the most efficient protocol we could found, that is binary. To be more precise we employ python’s cPickle binary protocol. Saying that the use of this is orders of magnitude more efficient is not even close

So after switching each subsystem to the new protocol we saw the load of the machines going down. As with all big changes in the backend of any system, it took a while to stabilize it. To avoid any havoc we actually put it into production subsystem by subsystem so during some time we had both protocols running at the same time.

And so, always remember that the choices you make will come to hunt you if not done correctly